Serial and other digital signals are often communicated as an analog signal consisting of a series of pulses representing binary symbols. Typically, the analog signal is sampled at discrete time intervals to extract the binary data. In an ideal system, the sampling is synchronized to be near the center of a pulse, but in practice the analog signal is subject to jitter. Jitter is the deviation of the significant instances of signal from its ideal position in time. If the jitter is sufficiently bad, the analog signal is sampled at the wrong side of a transition and a bit error may result.
Jitter may have a number of causes including random noise (thermal noise, shot noise and flicker noise in electronic components), system mechanisms (cross-talk from radiated or conducted signals, dispersion effects and impedance mismatches) and data-dependent mechanisms (inter-symbol interference, duty-cycle distortion). Jitter is usually categorized as being deterministic (or bounded) or random (unbounded). Deterministic jitter results from system and data-dependent mechanisms, while random jitter results from random noise.
Often a system designer or user is interested in the bit-error-ratio (BER) of a system. One method of estimating the BER requires knowing the magnitude of the random jitter and the magnitude of the deterministic jitter separately. Accordingly, methods have been developed to measure jitter in a signal and to decompose it into random and deterministic components.
Prior methods fit parametric models to measured time domain data (for example, tail-fitting to histograms) or use spectral methods (Fourier Analysis) applied to a single section of the signal.